Her Relentless Russian. Karev Brothers, #3

Rare bookstore owner Dmitry Karev left the Russian Mafia behind when his wife died, but there's too much at stake to keep his back turned any longer. His father is dead and his brothers may be next. Someone's been leaving Dmitry clues about the killer, but he never expected his informant to be a bombshell like Harper Allen. Now the curvy computer expert is testing not only Dmitry's methodical nature, but his self-restraint as well.
But with his family's lives in the balance, Harper may be the best chance Dmitry's got to catch a killer. When hacker Harper Allen's parents used her college money to pay off the Mafia, it was Sergey Karev who financed her education. Now that he's been murdered, she's repaying him the only way she can.by helping his son solve the crime. To follow the trail any further, though, she'll have to convince Dmitry to work with her.
The buttoned-up Russian seems hesitant at first, but it doesn't take long for Harper to discover what's beneath Dmitry's icy cool demeanor. As Harper and Dmitry worm their way deeper into the Russian Mafia, their chemistry becomes undeniable. But with a killer at their heels, they'll have to stay focused if they want to stay alive